Lighting systems in the prior art are typically formed by interconnecting, via a communications system, a plurality of lighting fixtures and providing for operator control of the plurality of lighting fixtures from a central controller. Such lighting systems may contain multiparameter light fixtures, which illustratively are light fixtures having two or more individually remotely adjustable parameters such as focus, color, image, position, or other light characteristics. Multiparameter lighting fixtures are widely used in the lighting industry because they facilitate significant reductions in overall lighting system size and permit dynamic changes to the final lighting effect. Applications and events in which multiparameter lighting fixtures are used to great advantage include showrooms, television lighting, stage lighting, architectural lighting, live concerts, and theme parks. Illustrative multi-parameter light devices are described in the product brochure entitled “The High End Systems Product Line 2001” and are available from High End Systems, Inc. of Austin, Tex.
A variety of different types of multiparameter light fixtures are available. One type of advanced multiparameter lighting fixture is an image projection lighting device (“IPLD”). Image projection lighting devices of the prior art typically use a light valve or light valves to project images onto a stage or other projection surface. A light valve, which is also known as an image gate, is a device for example such as a digital micro-mirror (“DMD”) or a liquid crystal display (“LCD”) that forms the image that is projected. Either a transmissive or a reflective type light valve may be used. U.S. Pat. No. 6,057,958, issued May 2, 2000 to Hunt, incorporated herein by reference, discloses a pixel based gobo record control format for storing gobo images in the memory of a light fixture. The gobo images can be recalled and modified from commands sent by a control console. A pixel based gobo image is a gobo (or a projection pattern) created by a light valve like a video projection of sorts. U.S. Pat. No. 5,829,868, issued Nov. 3, 1998 to Hutton, incorporated by reference herein, discloses storing video frames as cues locally in a lamp, and supplying them as directed to an image gate to produce animated and real-time imaging. A single frame can also be manipulated through processing to produce multiple variations. Alternatively, a video communication link can be employed to supply continuous video from a remote source.
IPLDs of the prior art use light from a projection lamp that is sent through a light valve and focused by an output lens to project images on a stage or a projection surface. The control of the various parameters of the IPLDs is affected by an operator using a central controller. In a given application, a plurality of IPLDs are used to illuminate the projection surface, with each IPLD having many parameters that may be adjusted by a central controller to create a scene.
IPLDs used in an entertainment lighting system can produce many colorful images upon the stage or projection surface. IPLDs may project images onto the projection surface such as still images, video images and graphic images. The term “content” is a general term that refers to various types of creative works, including image-type works and audio works. Content is typically comprised of still images, video images or loops and computer graphical images.
The Catalyst (trademarked) DL1 image projection lighting device manufactured by High End Systems of Austin Texas incorporates a video projector into an environmentally protective housing that can be remotely positioned to projected images to different locations upon the stage or projection surface. A personal computer is used as a server that provides the images to the DL1. A lighting controller sends command signals over a communication system to control the selection of images from the server to the projector as well as control the various functions of the DL1 and the position of the image on the projection surface.
IPLDs may project images such as video images or still images or they may project only light with no image. The projection of images by IPLDs is useful in creating a visual scene on the projection surface that can create an animation or a representation of objects. The projection of only light with no image on the projection surface such as white light or colored light is useful in providing illumination of the projection surface. Most often when illumination of the projection surface without images is required, the intensity of the illumination should be uniform across the projection surface.
U.S. Pat. No. 6,188,933 to Hewlett discloses “Another possible DMD effect is the simulation of a beam field distribution or profile, e.g., a cosine shaped profile for the spotlight.” The inventors in Hewlett recognized that spotlights are often overlapped with other spotlights at their edges. The area of overlap can cause a bright spot at those edges. The DMD is used to form a spotlight with edge portions that have intensities that are lower than the intensity in the center of the beam. The rate of intensity drop off is preferably a cosine function. In this way, when the two edge portions of two spotlights are placed one over the other, the overlap does not appear to be overly bright. However, such variable profiles will not be desired in all situations. A variable brightness profile will be desired in situations where multiple beams will be overlapping at their edges. However, other effects, such as illuminating a gobo, will be better illuminated using flat intensity profiles.”
A description of an invention for automatically adjusting the brightness uniformity of a plurality of image projection lighting devices is disclosed in US patent application “IMAGE PROJECTION LIGHTING DEVICES WITH PROJECTION FIELD LIGHT INTENSITY UNIFORMITY ADJUSTMENT” Ser. No. 10/319,366, filed on Dec. 13, 2002, by the inventor Richard S. Belliveau, incorporated by reference herein.
Varying the brightness profile on the projection surface by reducing the amount of light transmitted by or reflected from a light valve of an image projection lighting device is effective however only at the expense of an overall reduction of the light output or lumens onto the projection surface.